A transgender swimmer's team-mates have demanded she be banned from competitions over concerns that she will smash all their records.
Lia Thomas' team-mates want her banned from the upcoming NCAA swimming championships and have sent a letter to plead their case to US college sport bosses.
The letter, sent by Olympian Nancy Hogshead-Makar, is supported by 16 swimmers who have voiced their concerns over the advantage they claim Thomas has over them.
The issue has split the swimming team at the University of Pennsylvania, where Thomas competes as a woman despite swimming as a man just a few years ago.
Some of the Penn squad have supported her right to compete, but the 16 unnamed members who have backed the letter disagree.
They all say they fully support Thomas' gender identity, but argue that "the biology of sex is a separate issue from someone's gender identity" when it comes to sport and competition.
"Biologically, Lia holds an unfair advantage over competition in the women's category," they argue in the letter, before pointing out that Thomas shot from 462nd in the men's rankings to first among women.
"If she were to be eligible to compete against us, she could now break Penn, Ivy, and NCAA Women's swimming records – feats she could never have done as a male athlete.
"We support Lia's mental health, and we ask Penn and the Ivy League to support ours as well.
"Sport is competitive by definition, and Lia's wins, records, and honors should not come at our expense, the women who have worked their entire lives to earn a spot on the Penn Women's Swimming Team."
The women said they had purposely not revealed their identities as they had previously been warned that they would be kicked off the team if they spoke out against Thomas.
On Tuesday, USA Swimming introduced new guidelines which have a new threshold for the amount of testosterone in someone's body for them to be allowed to compete in women's competitions.
Thomas was not mentioned specifically in those guidelines, though the move has been seen as an attempt to make it more difficult for the 22-year-old to compete in major competitions.
In the letter, the 16 students asked the University of Pennsylvania not to go ahead with a legal challenge against those new guidelines as they want to "finish our swimming season with distinction and pride".
